It is known in the prior art to provide electronic control systems and methods for controlling the operation of an engine in a number of modes. Control systems are known that are capable of controlling fuel injection timing and quantity, and inlet and exhaust valve opening and closing independently for each engine cylinder, for example, for operating an engine in a Miller cycle mode, an exhaust gas recirculation (EGR) mode, as well as for operating an engine in either a four-cycle braking mode or a two-cycle braking mode.
In conjunction with the increasingly widespread use of electronic controls in engine systems, braking systems have been developed which utilize valve actuators that are electronically controlled by a central engine control unit. Compression release engine brakes are used to assist and supplement wheel brakes in slowing heavy machines, such as tractor-trailers. Engine brakes are desirable because they help alleviate wheel brake overheating. Known compression release engine brakes convert an engine from a power generating unit into a power consuming air compressor.
Existing engine braking systems often exhibit high noise levels and a lack of smooth operation at some braking levels resulting from the use of less than all of the engine cylinders in a compression release braking scheme. For example, U.S. Pat. No. 4,395,884 discloses a compression release engine brake that includes a selector switch for activating brake solenoids on selected engine cylinders. However, if less than all engine cylinders are used for compression release braking, and a certain cylinder or group of cylinders are used repeatedly for compression release braking, while another cylinder or group of cylinders is not used as often for compression release braking, the actuator and other components associated with each cylinder that is used repeatedly are likely to experience additional thermal cycling and/or wear, as compared to the components associated with each cylinder that is not used as often for compression release braking. Such thermal cycling and/or wear can lead to excessive noise (for example, due to clattering of valve train components), leakage of hydraulic components, and/or component failure.
The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.